There are a significant number of viruses that can infect swine. Such viruses include porcine reproductive and respiratory syndrome virus (PRRS), transmissible gastroenteritis virus (TGE), porcine pseudorabies virus (PPRV), porcine parvovirus (PPV), swine influenza virus (SIV), porcine rotavirus (PRV) and porcine epidemic diarrhea virus (PED). In addition, there are a number of bacteria that can infect swine too, including Pasteurella multocida of multiple serotypes, Salmonella ssp., Escherichia coli of multiple pillus types, Haemophilus parasuis, Lawsonia intracellularis, Mycoplasma ssp., Bordetella bronchiseptica, Erysipelas ssp., Campylobacter ssp., Actinobacillus pleuropneumoniae, Clostridium perfringens and Clostridium difficile. 
It is now widely accepted that the best way of preventing disease due to bacterial or viral infections in swine is to vaccinate them against these organisms. Moreover, multivalent live attenuated viral or bacterial vaccines can be safely administered that limit the number of vaccine injections required. Accordingly, there are many commercially available multivalent live virus vaccines that protect against multiple pathogens. However, heretofore, live attenuated swine viruses have been unstable when stored in liquid solutions. Therefore, most live attenuated swine virus vaccines are lyophilized, i.e., freeze-dried or frozen, prior to their long-term storage. The live attenuated porcine virus is commonly mixed as a suspension in water with a protective agent, frozen, and then dehydrated by sublimation and secondary drying during the lyophilization process. The low temperatures of freezing and drying by sublimation, together with the low surface to volume ratios involved, can require long drying periods and thereby, significantly increase manufacturing time and costs.
In addition, there are inherent inconsistencies in large commercial drying processes due to: the inability to adjust the shelf temperature across the entire product load, variable freezing rates across the dryer, edge effects, and radiant energy effects. Increasing the drying temperature to reduce drying times is often not an option since the drying temperature has to remain significantly below the glass-transition temperature of the protective protein matrix. Moreover, the long inconsistent drying times and/or high drying temperatures often lead to structural damage to the live attenuated viruses, along with a significant loss of their biologic activity.
Consequently, in order to account for the inherent loss in efficacy, lyophilized swine vaccines that comprise live attenuated viruses are manufactured with augmented titers. However, such increased titers can lead to significant adverse events should the lyophilization process actually lead to less loss of activity than anticipated. This is particularly problematic for the swine farmer because, at minimum, such an adverse event often leads to lower daily weight gain for the pigs, which translates to lower profits at sale. Therefore, great care is required to formulate a vaccine to contain a virus titer that is not only safely below the amount that leads to adverse events, but that also maintains sufficient efficacy in view of the virus titer loss due to lyophilization and subsequent storage.
Furthermore, there is a limitation to the size of a lyophilization vials and/or number of doses contained within such vials due to relatively small standard stopper sizes for the tops of these vials. Therefore, large volumes of liquid become difficult to sublimate through the relatively small openings. Therefore, there is a need for new live attenuated porcine virus vaccines that can reliably retain their virus titers at a safe and efficacious level.
Additionally, it is not economical to produce swine vaccines in single dose vials. However, vials of lyophilized vaccines must be used in their entirety after rehydration of the freeze dried cake. This makes it difficult for the growing number of small swine farmers who cannot take advantage of the economics of a larger package presentation with a greater number of doses to vaccinate only a few pigs. There is therefore a need for swine vaccines where a single vial can be used over multiple days, weeks or even months, thus reducing the cost and encouraging vaccination of smaller herds.
Finally, due to the nature of lyovials, there is a limitation to the size of the vial and the amount of the liquid that can be lyophilized within. This means that large production facilities must rehydrate multiple bottles in order to vaccinate hundreds, if not thousands of pigs at a time. Once rehydrated in the glass vials, in accordance to the regulations for live vaccine organisms, the glass vials themselves become hazardous waste and must be sterilized or disinfected, buried or burned. Sterilization becomes difficult on the swine farm and often these vials are just discarded into the trash. On the other hand, the use of a liquid stable vaccine would not need to be restricted by being placed into small glass containers, but rather the vaccine could be stored in plastic bags that could have a large range in sizes. Moreover, following the administration of the vaccine to the swine, the plastic bags can easily be destroyed by burning in a small contained fire.
The citation of any reference herein should not be construed as an admission that such reference is available as “prior art” to the instant application.